Stihl 4180 Series Service Manual

Series 4180 Powerhead6
3.4 Carburetor
Condition Cause Remedy
Carburetor floods, engine stalls Inlet needle not sealing. Foreign matter in
valve seat or cone damaged
Remove and clean the inlet needle, clean
the carburetor
Inlet control lever sticking on spindle Free off inlet control lever
Helical spring not located on nipple of inlet
control lever
Remove the inlet control lever and refit it
correctly
Inlet control lever too high (relative to cor-
rect installed position)
Fit new inlet control lever
Poor acceleration Idling or full load setting too lean Readjust the carburetor
Inlet control lever too low (relative to cor-
rect installed position)
Fit new inlet control lever
Inlet needle sticking to valve seat Remove inlet needle and clean valve seat
Diaphragm gasket damaged Fit new diaphragm gasket
Metering diaphragm damaged / shrunk /
hardened
Fit new metering diaphragm
Engine will not idle, idle speed too
high
Throttle shutter opened too wide by idle
speed screw (LA)
Reset idle speed screw (LA) correctly
Throttle shutter is not closed properly even
when idle speed screw (LA) is backed off
all the way
Check throttle cable
Engine leaking Test engine for leaks
Engine stops while idling Idle jet bores or ports blocked Clean the carburetor
Setting of low speed screw (L) too rich or
too lean
Reset low speed screw (L) correctly
Setting of idle speed screw (LA) incorrect –
throttle shutter completely closed
Reset idle speed screw (LA) correctly
Engine speed drops quickly under
load – low power
Air filter dirty Clean or replace air filter
Exhaust port / muffler carbonized Clean exhaust port / muffler, fit new muffler
if necessary
Throttle shutter is not opened fully Check throttle cable
Tank vent faulty Test the tank vent, replace if necessary
Fuel pickup body dirty Clean the pickup body, replace if
necessary
Leak in a fuel hose Check fuel hoses and replace if necessary
Fuel strainer in carburetor dirty Clean fuel strainer in carburetor, replace if
necessary
Setting of high speed screw (H) too rich Readjust the carburetor
Pump diaphragm damaged / shrunk /
hardened
Fit new pump diaphragm

Stihl 4180 Series Specifications

General

Brand	Stihl
Model	4180 Series
Category	Engine
Language	English